This invention relates to support systems such as mattresses, cushions and the like, characterized by having a liquid within them, as, for example in waterbeds.
It is well-known that various benefits can be obtained by making waterbeds and other support systems having a liquid within them. Yet, these systems are subject to certain well-known shortcomings. First, conventional waterbeds and cushions produce a kind of wave action or rolling motion when in use due to the tendency of the water inside to rush rapidly from one part of the mattress to another. As a person places his weight on one portion of the support system, the water or other liquid is forced to flow to another part of the system. Since the envelope containing the liquid is typically elastically yieldable, there will be a reaction to the initial surge of liquid which will result in a succession of countersurges back and forth within the envelope until the system finds equilibrium. This undamped surging and countersurging of the liquid within mattresses is annoying to most people and actually produces motion sickness in some of them. To overcome this, many waterbed manufacturers do not use liquid displacement in that portion of the waterbed which is intended to support one's head and shoulders. Instead, they use a section of standard mattressing employing coil springs or equivalent non-liquid structures. Needless to say, this introduces an element of complexity to the manufacturing process. Other manufacturers have attempted to dampen waterbed wave motion in various ways. In U.S. Pat. No. 3,585,356, the use of solid particles, such as Styrofoam, are disposed in the liquid for this purpose. U.S. Pat. No. 3,736,604 uses flap means, as illustrated in FIG. 11 therein.
Another disadvantage associated with conventional liquid displacement support systems is that they are relatively unstable in the sense that they tend to react too quickly in response to the application or shifting of one's weight on them. If, for example, a person lying on a mattress attempts to roll over, he will find that the mattress yields rather quickly under him as he presses against it with one of his limbs to initiate movement. The bed sort of undulates under him as the water surges about within the mattress. Similarily, as one attempts to get out of bed, there is a feeling of instability since the mattress quickly gives way as his weight is shifted to its edge. This kind of instability is further illustrated when a water cushion is used on a conventional chair or on the seat of an automobile or a wheelchair. When used on a conventional chair, the instability is manifested most clearly as a person attempts to stand. The water is quickly displaced within the cushion as the person's weight is shifted and he has the feeling that the cushion is squirting out from under him as he attempts to thrust his body upwardly. The normal rocking motion of a moving automobile or wheelchair is greatly amplified by conventional water cushion systems for the same reasons.
Still another disadvantage associated with conventional liquid displacement support systems concerns the requirement that these systems be used for the most part in a horizontal disposition. The reason for this is that if a relatively elongated support unit is disposed vertically or at some considerable angle to the horizontal, the liquid will be drawn by gravity to the lower portions causing bulging in those areas while lowering or completely eliminating the cushioning and supportive effects in the upper areas. Thus, such systems are of limited usefulness as backrests or in hospital beds where a portion of the bed needs to be tilted at an angle to the horizontal.
Perhaps the most obvious disadvantage associated with conventional liquid displacement systems is their weight. Since substantially the entire interior of the liquid cell is filled with a liquid, its overall weight is very considerable.
It would, of course, be desirable if a liquid displacement support system could be constructed in which the above-described disadvantages would be eliminated.
I have discovered that these disadvantages, in fact, can be overcome in a system using a reduced amount of liquid, the movement of which is damped by providing a core of flexible cellular material.
It is, therefore, an object of this invention to provide a liquid displacement support system in which the movement of liquid from one point to another in the support device is damped and modulated.
It is a further object of this invention to provide a liquid displacement support system which will present a relatively stable support structure which will not exhibit the familiar undesirable flowing wave motion.
It is a further object of this invention to provide a low volume liquid displacement support system which will be considerably lighter in weight than systems heretofore known.
It is still another object of this invention to provide a liquid displacement support system in which an elongated support element can be used in a vertical position without significant bulging in its lower regions or loss of support in its upper regions.
It is another object of this invention to provide a damped liquid displacement support system which can be used as a full length mattress without the need to use any special structures under the user's head for the elimination of motion sickness.
These and other objects of the invention are accomplished by enclosing a core of resilient liquid-absorbent material within a liquid-sealed envelope, the core being saturated with a liquid. In other words, a liquid-tight envelope is provided in which the interior is substantially completely occupied by a core of resilient, liquid-absorbent material, said core being substantially saturated with a liquid.
The method used to fabricate support systems according to the present invention comprises the steps of placing a core of resilient, liquid-absorbent material within an unsealed envelope of liquid impervious material, compressing the envelope and the core so as to force substantially all gases therefrom, sealing the envelope, submerging the envelope and core in a liquid and temporarily opening the envelope while submerged to admit liquid until the core is substantially saturated.